1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and particularly to a technique for burying a contact hole or the like.
2. Description of the Related Art
According to a conventional technique for burying a contact hole or the like, an insulating film (such as an SiO2 film, a BPSG film) is formed over an IC substrate. Thereafter, a contact hole is defined therein by photolithography and etching. Further, a contact or adhesive layer comprised of titanium (Ti) film, a titanium nitride (TiN) film or their layered film or the like is deposited over the insulating film. Afterwards, a tungsten film (CVD-W film) is deposited by a chemical vapor deposition method so as to be embedded in the contact hole. The process of growing or depositing the CVD-W film is roughly divided into two. A first step aims to form the nucleus of tungsten over the adhesive layer. The CVD-W film is deposited with tungsten hexafluoride (WF6), monosilane (SiH4) and hydrogen (H2) principally as main materials.
The sequence of the first step is as follows. A semiconductor wafer is placed in a pressure-reduced chamber and the temperature in the chamber is increased to a deposition temperature. Next, WF6 and SiH4 used as material or raw gases are introduced therein to form a thin film of tungsten, which is called xe2x80x9cnucleus formationxe2x80x9d. In a second step, SiH4 is cut off and a CVD-W film good in step coverage is deposited with WF6 and H2 principally as main materials. After the CVD-W film has been embedded in the contact hole, the CVD-W film is left only within the contact hole by full-face etchback.
With a reduction in temperature for the manufacture of an LSI and an improvement in step coverage, there has recently been an increasing demand for the deposition of the CVD-W film under a low-temperature condition.
However, the deposition of the CVD-W film under the conventional low-temperature condition might develop abnormal growth of a protrusion or the like considered to be composed principally of tungsten at a stage corresponding to the first step, for performing the formation of the nucleus of tungsten over the adhesive layer. The magnitude of the abnormal growth of the protrusion or the like is a size close to the diameter of the contact hole and it is grown from above the adhesive layer. Therefore, when the abnormal growth is developed on the contact hole in the first step, a W film is actually deposited in the next step. However, the abnormal growth blocks the contact hole so that the deposition gases do not enter into the contact hole, thus causing an embedment failure in contact hole. The presence or absence of the occurrence of the abnormal growth in the first step differs according to the type of adhesive layer. Namely, it greatly depends on the state of the surface of the adhesive layer. Particularly when the surface of the adhesive layer is oxidized upon the subsequent heat treatment, WF6 and SiH4 used the deposition gases are not absorbed into the surface of the adhesive layer in the first step at the deposition of the CVD-W film. Therefore, an Incubation Time becomes long and the abnormal growth occur.
Incidentally, the Incubation Time indicates a deposition delay time during which while a material gas flows into a chamber in the first step, a CVD-W film is not deposited over a wafer till a given time that elapsed since it has flowed therein. A problem arises in that when the Incubation Time becomes long, abnormal growth occurs during the Incubation Time and blocks a hole, so that an embedment failure in hole occurs.
An object of the present invention is to provide a method of manufacturing a semiconductor device, which is capable of inhibiting abnormal growth at the deposition of a CVD-W film and reducing an embedment failure in contact hole due to the abnormal growth.
According to one aspect of the invention, for achieving the above object, there is provided a method of manufacturing a semiconductor device, comprising a step for forming an insulating film over a semiconductor wafer and thereafter subjecting the same to photolithography and etching to thereby define a contact hole, a step for forming an adhesive layer over the insulating film with the contact hole defined therein, a step for placing the interior of a processing chamber under an atmosphere that does not contain oxygen and subjecting the adhesive layer to heat treatment, a step for setting the temperature of the semiconductor wafer to less than or equal to a temperature equivalent to energy of such an extent as to cut the bonding between atoms which form the adhesive layer and thereafter taking the semiconductor wafer out of the processing chamber, and a step for forming an embedding film to be embedded in the contact hole.
Typical ones of various inventions of the present application have been shown in brief. However, the various inventions of the present application and specific configurations of these inventions will be understood from the following description.